Smart/wearable devices for body temperature tracking are becoming more and more challenging based on traditional temperature sensing technologies. Electronic sensors for temperature are typically composed of tiny tips of negative temperature coefficient (NTC) ceramic materials, platinum (PT-100) or infrared photo-devices. These electronic sensors don't have enough accuracy for temperature sensing when becoming wearable on a human body since the thermal contact area is limited. It is challenging for these sensors to build up thermal equilibriums with the human body under ambient environments, and thus these thermometers take a very long time to measure the body temperature, such as 10-15 min or much longer. There are also some flexible thin films of platinum sensors for temperature but their area is limited to 1 mm-2 mm since Pt is quite expensive. Therefore, it is very difficult for traditional sensors to continuously monitor and track physiological signals as smart/wearable devices, especially when biometric information on the human body almost changes every second.